Air filter, local facility, and clean room

ABSTRACT

A material not releasing gaseous organic substances during use is used as a filter medium and a sealing material for tightly sealing between the medium and a frame. Specifically, a synthetic paraffin not containing an aliphatic hydrocarbon having not more than 19 carbon atoms or less is used as a non-silicone type water repellent contained in a treatment agent for forming fibers into a cloth-like filter medium. A carboxylic acid ester having 400 or more molecular weight is used as a plasticizer and a phenolic compound having 300 or more molecular weight is used as an antioxidant to be added to the treatment agent and the sealing material. This enables that the gaseous organic substances are not present in a clean room, in a semiconductor production apparatus or in the like. Further, if the filter medium and the sealing material are formed of a material not releasing organic phosphorus compounds and boron compounds in the air, a clean room and a local facility particularly suitable for use in the production of semiconductors are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 08/817,007, filed Mar.27, 1997, now U.S. Pat. No. 5,997,598, which was filed under 35 U.S.C.371 as the national stage application of PCT/JP96/02076, filed Jul. 25,1996, and published as WO97/04851 on Feb. 13, 1997.

FIELD OF THE INVENTION

The present invention concerns an air filter for use in a clean roomused, for example, in factories or research laboratories relevant to thefield of semiconductors, in food-stuffs and biotechnology, in a methodof manufacturing thereof, in a local facility, and in a clean roomequipped with the air filter.

BACKGROUND OF THE INVENTION

In clean rooms used in factories or research laboratories in therelevant field of semiconductors, in foodstuffs, in medicines, and inbiotechnology, dry air filters for trapping air-born particles aredisposed to air introduction paths, and air passing therethrough isintroduced into the clean room.

Air filters currently used in clean rooms include ULPA (abbreviation forUltra Low Penetration Air) with uses glass fibers for the filter mediumand HEPA (abbreviation for High Efficiency Particle Air), Such filtersare excellent for removing dusts, for example, ULPA filters can removefine particles as small as 0.1 μm. Further, non-glass type filters withfluoro resin or quartz fibers, instead of the glass fibers, for thefilter medium have been developed so as not to release inorganicsubstances from the air filters.

Recently, with the increase of integration degree of semiconductors,diffusing gaseous organic substances as well as dusts from the cleanroom air has been considered to be the cause of defects. It has beenpointed out that organic substances are adsorbed on the surface ofsemiconductor substrates (silicon wafers) in clean rooms, deterioratingdevice characteristics (Fujii, “Gaseous Contaminants and CurrentSituation for Countermeasure of Removal”, Air Cleaning, Vol. 32, No. 3,p 43 (1994), published from the Foundation of Japan Air CleaningSociety).

Further, it has been well known that an n-type semiconductor is obtainedby doping P (phosphorus), and a p-type semiconductor is obtained bydoping B (boron) into a silicon wafer in semiconductor manufacturingsteps However, if phosphorus compounds or boron compounds are present inthe clean room air, these may cause unnecessary doping, so that it isnecessary to remove such ingredients from the clean room air.

The present invention has been developed to solve the problems describedabove and it is an object thereof to provide an air filter for trappingair-born particles that can eliminate the presence of gaseous organicsubstances, for example: in clean rooms, semiconductor productionapparatus’ or the like, a method of manufacturing an air filtertherefor, a treatment agent constituting the air filter, a method ofmanufacturing a filter medium, a clean room and a local facility, suchas a semiconductor production apparatus, in which gaseous organicsubstances are not present; as well as in a clean room and a localfacility in which phosphorus compounds and boron compounds are notpresent.

DISCLOSURE OF THE INVENTION

The present inventors have made earnest studies for attaining theforegoing object and, as a result, have accomplished the presentinvention based on the finding that presence of gaseous organicsubstances in a clean room and a local facility, such as a semiconductorproduction apparatus, is mainly caused by air filters disposed to airintroduction paths and gaskets intervened for attaching the air filtersto openings, for example, in a ceiling.

It has been found by the study of the present inventors that gaseousorganic substances, such as cyclosiloxanes, carboxylic acid esters,phosphoric acid esters, hydrocarbons, and phenols, are released from theexistent air filters described above. These organic substances are alsoreleased from treatment agents impregnated between each of the fibersupon forming the fibers into a cloth-like filter medium (including abinder for binding fibers, a water repellent for improving dust trappingeffect, and a plasticizer or an antioxidant), silicone oils deposited tofibers in a case where the filter medium is glass fibers (this is areinforcing material upon spinning glass fibers which serves also as awater repellent of the filter medium) and sealing materials for bondinga filter medium and a frame. Further, it has been found that organicsubstances are detected at a high ratio from rubber materials used asgaskets.

Specifically, it has been found that the ingredient of the conventionalwater repellent (non-silicone type) in the treatment agent is liquidparaffins (aliphatic hydrocarbon having 12 to 18 carbon atoms) whichcontain a plasticizer or an antioxidant of relatively low molecularweight. When the sealing material comprising a polyurethan resin as themain ingredient is used, specifically in the case of a two componentpolyurethane resin, isocyanates of the main agent left after the curingreaction become organic contaminations. When the sealing materialcomprising an epoxy-type resin is used, specifically in a case of a twocomponent epoxy resin, amine compounds used as a curing agent becomeorganic contaminations. It has also been found that conventional sealingmaterials contain plasticizers and antioxidants of relatively lowmolecular weight.

Based on the findings described above, the present invention provides anair filter comprising a filter medium of fibers treated with a treatmentagent formed into a cloth-like shape, a frame for containing the filtermedium, and a sealing material for tightly sealing a portion between theframe and the filter medium in order to trap air-born particles, whereinat least one of the filter medium and the sealing material does notrelease gaseous organic substances during use.

Further, the present invention provides an air filter satisfying one ofthe following definitions (a)-(c) and (e)-(g) for the treatment agentand the sealing material.

(a) The main ingredient of a non-silicone type water repellent containedin the treatment agent is at least one of an aliphatic hydrocarbonhaving 20 carbon atoms or more and a higher alcohol having 18 carbonatoms or more.

(b) The main ingredient of the plasticizer contained in the treatmentagent is at least one of carboxylic acid esters, polyester, and epoxytype compound having 400 or more molecular weight.

(c) The main ingredient of the antioxidant contained in the treatmentagent is a phenolic compound having 300 or more molecular weight.

(e) The main ingredient of the plasticizer contained in the sealingmaterial is at least one of carboxylic acid esters, polyesters, andepoxy type compounds having 400 or more molecular weight.

(f) The main ingredient of the antioxidant contained in the sealingmaterial is a phenolic compound having 300 or more molecular weight.

(g) The main ingredient of the lubricant contained in the sealingmaterial is at least one of an aliphatic hydrocarbon having 20 carbonatoms or more and a higher alcohol having 18 carbon atoms or more.

Further, the present invention provides a method of manufacturing an airfilter which comprises selectively using the plasticizer and theantioxidant defined in (b), (c), (e), and (f) for the treatment agentand the sealing agent described above.

If the main ingredient of the non-silicone type water repellent in (a)and the main ingredient of the lubricant in (g) are an aliphatichydrocarbon having 19 carbon atoms or less and a higher alcohol having17 carbon atoms or less, gaseous substances are present in the cleanroom air being entrained by air passing through the air filter in ausual clean room, which is controlled at a temperature of 23° C. and ata humidity of 30-40% and in which the flow rate of air passing throughthe air filter is about 0.3 to 0.4 m/s. However, such gaseous substancesare not present in the clean room air when an aliphatic hydrocarbonhaving 20 carbon atoms or more and a higher alcohol 18 having carbonatoms or more is used.

Further, if the main ingredient of the plasticizer in (b) and (e) isdibutyl phthalate (molecular weight 278), dioctyl phthalate (molecularweight 391), or di-2-ethylhexyl adipate (molecular weight 371) having400 or more molecular weight, the gaseous substances are present in theclean room air being entrained by air passing through the air filter inthe usual clean room, but the gaseous substances are not present in theclean room air if those having 400 or more molecular weight are used.

Further, if the main ingredient of the antioxidant in (c) and (f) is2,6-di-t-butyl-p-cresol (molecular weight 220.4) having 300 or moremolecular weight, the gaseous substances are present in the clean roomair being entrained by air passing through the air filter in the usualclean room, but the gaseous substances are not present in the clean roomair if those having 400 or more molecular weight are used.

Actual examples of (a) and (g), can be at least one of microcrystallinewax, natural wax, synthesis paraffin, polyolefin wax, branched alcoholof 18, 20, and 24 carbon number, and oleyl alcohol.

Actual examples of (b) and (e), can be isononyl phthalate (molecularweight: 418), octyldecyl phthalate (molecular weight: 419), diisodecylphthalate (molecular weight: 447), lauryl phthalate (molecular weight:501), myristylyl phthalate (molecular weight: 530), di-2-ethylhexylazelate (molecular weight: 413), di-2-ethylhexyl sebacate (molecularweight: 427), tris-2-ethylhexyl trimellitate (molecular weight: 547),trioctyl trimellitate (molecular weight: 547), trinonyl trimellitate(molecular weight: 570), tridecyl trimellitate (molecular weight: 612),polyesters obtained by polycondensation of adipic acid, azelaic acid,sebacic acid, or phthalic acid and glycol or glycerine (molecularweight: 2,000-8,000), epoxy fatty acid ester (molecular weight:400-500), and epoxidized oil (molecular weight about 1,000).

Actual examples of (c) and (f), can bestearyl-β-8-(3,5-di-t-butyl-4-hydroxyphenyl) propionate (molecularweight: 520.9), 2,2′-methylene-bis (4-methyl-6-t-butylphenol) (molecularweight: 340.5), 2,2′-methylene-bis (4-ethyl-6-t-butylphenol) (molecularweight 368.54), 4,4′-thiobis (3-methyl-6-t-butylphenol) (molecularweight: 358.5), 4,4′-butylidene-bis (3-methyl-6-t-butyl-phenol)(molecular weight: 382.6), 1,1,3-trls(2-methyl-4-hydroxy-5-t-butylphenyl) butane (molecular weight: 544.8),1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene(molecular weight: 775.2), tetrakis(methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl) propionate methane(molecular weight: 1177.7), bis (3,3′-bis (4′-hydroxy-3′-t-butylphenyl)butiric acid) glycol ester (molecular weight: 1177.7), and tocophenol(molecular weight: 794.4).

Further, the present inventors have found that as the molecular weightof the organic substance is greater, the volatility is lowered and theadsorption property is increased. However, the adsorption amount to thesilicon wafer is decreased and restricted if the molecular weightincreases to more than a predetermined amount and that the predeterminedamount is different depending on the molecular structure, anddefinitions for the numerical values in (a)-(c) and (e)-(g) describedabove were determined based on the result of an experiment conducted fora number of targeted materials respectively.

The air filter according to the present invention may satisfy at leastone of the definitions (a)-(c) and (e)-(g) described above, but thosesatisfying all of them are preferred since no gaseous organic substancesare released from all of the constituent materials of the air filter.

Specifically, preferred are those in which the main ingredient of thenon-silicone type water repellent is microcrystalline wax, the mainingredient of the plasticizer contained in the non-silicone series waterrepellent is tri-2-ethylhexyl trimellitate, the main ingredient of theantioxidant contained in the non-silicone type water repellent is2,2′-methylene-bis (4-ethyl-6-t-butylphenol), the main ingredient of theplasticizer contained in the sealing material is di-2-ethylhexylsebacate, the main ingredient of the antioxidant contained in thesealing material is 2,2′-methylene-bis (4-ethyl-6-t-butylphenol), andthe main ingredient of the lubricant contained in the sealing materialis synthesis paraffin.

Further, the present invention provides an air filter which satisfies atleast one of the definitions (a)-(c) and (e)-(d) described above, inwhich the main ingredient of the sealing material is a two componentpolyurethane resin formed by reaction between a main agent comprising apolyisocyanate and a curing agent, and the equivalent amount of activehydrogen in the curing agent is more than the equivalent amount of theisocyanate as the main agent and which contains no phosphoric acidester. In the air filter, since the isocyanates of the main agent do notremain after the curing reaction of the sealing material, isocyanatesand diamines caused by reaction of the isocyanate with water in the airare not formed, and since phosphoric acid ester is not released, releaseof gaseous organic substances from the sealing material is furthersuppressed.

The present invention further provides an air filter which satisfies atleast one of the definitions (a)-(c) and (e)-(g) described above and inwhich the main ingredient for the sealing material is a two componentepoxy resin formed by the reaction between the main ingredient and thecuring agent, and the curing agent is acidic or neutral. In the airfilter, since a basic amine compound as the curing agent of the sealingmaterial is not contained in the air filter, release of the gaseousorganic substances from the sealing material is further suppressed.

The present invention further provides an air filter which satisfies atleast one of the definitions (a)-(c) and (e)-(g) described above and inwhich the main ingredient of the sealing material is a two componentepoxy resin formed by the reaction between the main agent and the curingagent. The resin is of an amine type and the residual amine is reduced.As the means for reducing the residual amine, there can be blending andcuring such that the amine equivalent is slightly lower than the epoxyequivalent thereby leaving no residual amine after curing, or heatingthe resin after curing thereby volatilizing the residual amine.

Further, the present invention provides an air filter which satisfies atleast one of the definitions (a)-(c). and (e)-(g) described above and inwhich the filter medium is formed into a cloth-like shape by treatingsilicone-oil deposited glass fibers with a treatment agent and thesilicone oil does not contain cyclosiloxanes having 10 silicon atoms orless. Since cyclosiloxanes having 10 silicon atoms or less are adsorbedextremely easily to the silicon wafer, this filter is partticularlysuitable, to an air filter used for a clean room for use insemiconductor production.

Further, the present invention provides a method of manufacturing an airfilter including a first step of depositing a silicone oil to glassfibers and a second step of treating the glass fibers with a treatmentagent, thereby forming a cloth-like filter medium. This method comprisessubjecting the glass fibers, after the first step, to a heat treatmentin a clean air stream, thereby sufficiently removing siloxanes having 10silicon atoms or less from the silicone oil deposited to the glassfibers and then applying a treatment by a treatment agent not releasinggaseous organic substances.

This is one of methods for manufacturing the air filter, in whichsiloxanes having 10 silicon atoms or less contained in the silicone oilcan be removed sufficiently by putting the glass fibers deposited withthe silicon oil in a tightly closed vessel and heating, for example, at120° C. for several hours.

Further, the present invention provides a method of manufacturing an airfilter including a first step of depositing a silicon oil to glassfilters and a second step of treating the glass fibers with a treatmentagent, after the first step into a cloth-like filter medium whichcomprises using those removed with cyclosiloxane having 10 silicon atomsor less as the silicone oil used in the first step and treating them bya treatment agent not forming gaseous organic substances.

This is one of methods for manufacturing the air filter. Siloxaneshaving 10 silicon atoms or less contained in the silicone oil can beeliminated sufficiently by removing low boiling ingredients by heating,for example, at 200° C. in a vacuum state (for example, at vacuum degreeof 5 mHg).

Further, the present invention provides a clean room equipped one of theair filters described above.

The present invention also provides a local facility equipped with oneof air filters described above. The local facility means a clean boothdisposed to a place where cleanness is intended to be increased locally,or a production facility requiring a predetermined cleanness, forexample, a semiconductor production apparatus.

Further, the present invention provides a clean room, in which walls andfloors are fabricated with building materials releasing gaseous organicsubstances in an amount of 50 μg per 1 g or less measured by a purge &trap method. One of the air filters described above is attached byinterposing, between the air filter and an opening used for attachment,a gasket not releasing gaseous organic substances in an amount of 50 μgper 1 g or less measured by the purge & trap method.

When the walls and the floors of the clean room and the gaskets forattaching the air filters are constituted with materials releasinggaseous organic substances in an amount of 50 μg per 1 g or lessmeasured by the purge & trap method, the clean room can be reliably putto a state in which the organic substances are not released in a usualoperation state.

If the clean room is used, for example, in a semiconductor productionfactory, it is possible that the organic substances are scarcelyadsorbed to the silicone wafer.

The purge & trap method is a method of passing an inert gas at apredetermined temperature (a temperature at which all the organicingredients can be volatile) to a predetermined amount of a material,evaporating all the gaseous organic ingredients contained in thespecimen, trapping them and quantitatively determining the amount of thegaseous organic substances released from the trapped ingredient.

For the wall materials among the building materials releasing thegaseous organic substances in an amount of 50 μg per 1 g or less, amethod of dry sealing a partition system by a fire proof materialpreviously proposed by the present applicant (refer to Patent Laid-OpenSho 62-86248, Utility Model Laid-Open Sho 62-56614 and Utility ModelLaid-Open Sho 62-124102) can be adopted and the surface material of thefree access floor may be made of inorganic material such as stainlesssteel. The amount of gaseous organic substances released from the wallmaterials and the floor materials is about 1.0 μg per 1 g.

Further, the present invention provides a treatment agent forimpregnation into fibers in order to form the fibers into a cloth-likeshape as a filter medium used for the air filter, which satisfies one ofthe definitions (a)-(c) described above. The treatment agent cansuppress the amount of gaseous organic substances released from the airfilter manufactured by using them.

As the treatment agent, those satisfying all the definitions (a)-(c)described above are preferred since gaseous organic substances are notreleased from the main constituent materials.

Further, the present invention provides a method of manufacturing afilter medium which selectively uses those defined with (b) and (c)described above as the plasticizer and the antioxidant contained in thetreatment agent impregnated in the filter medium. According to thismethod, a filter medium with less releasing amount of the gaseousorganic substances can be manufactured.

The present inventors have further found that the presence of thephosphorus compounds or boron compounds in the clean room isattributable to organic phosphorus compounds (phosphoric esters)contained in the sealing material tightly sealing a portion between thefilter medium and the frame of the air filter and surface material forwalls and floors for the phosphorus compounds, and attributable to boronoxides contained in glass fibers as the filter medium of the air filterfor the boron compounds.

From the findings described above, the present invention provides aclean room in which at least the surface material of the walls and thefloors, the filter medium of the air filter and the sealing material fortightly sealing the portion between the filter medium and the frame, areformed of a material so as to not release organic phosphorus compoundsand boron compounds into the air.

Further, the present invention provides a clean room in which thematerial releases gaseous organic phosphor compounds in an amount of 10μg or less per 1 g of the material by the purge & trap method andleaches boron compounds in an amount of 20 μg or less per 1 g of thematerial after immersing in ultra-pure water for 28 days.

As described above, even when the constituent materials for the cleanroom are formed of a material containing the organic phosphoruscompounds and the boron compounds, if the amount of the gaseous organicphosphorus compounds released from the constituent material is reducedto 10 μg or less per 1 g by the purge & trap method, and the boroncompounds leached after immersion in ultra-pure water for 28 days isreduced to 20 μg or less per 1 g, it is possible that the organicphosphorus compounds and the boron compounds are not present in theclean room air when the clean room is operated in a usual state (at atemperature of 23° C., humidity of 30-40% and a flow rate of air passingthe air filter of 0.3-0.4 m/s).

Further, the present invention provides a clean room in which thesealing material is a polyurethane resin type sealing materialcontaining diphenyl methane diisocyanate as a diisocyanate constitutingthe main ingredient thereof, and when a phosphoric acid ester iscontained as a liquefying agent therefor, the molecular weight of thephosphoric acid ester is determined as 300 or more.

In conventional clean rooms, phosphoric acid esters are used as theliquefying agent for the polyurethane resin type sealing materialcontaining diphenyl methane diisocyanate (additive for making diphenylmethane diisocyanate at high purity into a liquid state at a normaltemperature) and as a plasticizer or a flame retardant for the vinylchloride resin type sheet as the surface material for the walls and thefloors. Carboxylic acid or the like, having 400 or more molecular weightshown in (e) described above, can be used instead of the phosphoricacid, and aluminum hydroxide, antimony trioxide or the like can be usedinstead of the phosphoric acid ester for the flame retardant. There isno substitute for the phosphoric acid ester as the liquefying agent. Ifthe phosphoric acid ester used is triethyl phosphate (molecular weight182), tributyl phosphate (molecular weight 266), and tris(β-chloroethyl) phosphate (molecular weight 285) having 300 or lessmolecular weight, gaseous substances of them are entrained by airpassing through the air filter and present in the clean room air in theusual clean rooms described above, but, when those having 300 or moremolecular weight are used, gaseous substances of them are not present inthe clean room air.

Accordingly, it is possible that the phosphoric acid ester will not bepresent in the clean room air by using a phosphoric acid ester having300 or more molecular weight as the liquefying agent and by using thesubstitute described above or a phosphoric acid ester having 300 or moremolecular weight for the plasticizer and the flame retardant.

Further, the present invention provides a clean room in which thephosphoric acid ester used as the liquefying agent is at least one ofthe substances shown in (h) below. (h) tri-2-ethylhexyl phosphate(molecular weight 435), tributoxyethyl phosphate (molecular weight 398),trioleyl phosphate (molecular weight 849), triphenyl phosphate(molecular weight 326), tricresol phosphate (molecular weight 368),trixylenyl phosphate (molecular weight 410), cresyl phenyl phosphate(molecular weight 340), xylenyl diphenyl phosphate (molecular weight354), 2-ethylhexyl diphenyl phosphate (molecular weight 362), condensedaromatic phosphoric acid ester (molecular weight not less than 400).tris(tridecyl)phosphite (molecular weight 629), and triphenyl phosphite(molecular weight 310).

Further, the present invention provides a local facility in which atleast the surface material for the walls, the filter medium for the airfilter, and the sealing material which tightly seals a portion betweenthe filter medium and the frame are formed of a material not releasingorganic phosphorus compounds and boron compounds in the air.

Further, the present invention provides a local facility in which thematerial releases gaseous organic phosphorus compounds in an amount of10 μg or less per 1 g of the material by the purge & trap method, andleaches the boron compound in an amount of 20 μg or less per 1 g of thematerial after immersing in ultra-pure water for 28 days.

Further, the present invention provides a local facility in which thesealing material is a polyurethane resin type sealing material, containsdiphenyl methane diisocyanate as a diisocyanate constituting the mainingredient thereof, and when the phosphoric acid ester is contained asthe liquefying agent therefor, the molecular weight of the phosphoricacid ester is 300 or more.

Further, the present invention provides a local facility in which thephosphoric acid ester used as the liquefying agent is at least one ofthe substances shown in (h).

As described above also in the local facility, it is possible that thegaseous organic phosphorus compounds or boron compounds are not presentin the air at the inside of the local facility by constituting the wallmaterial and the air filter in the same manner as in the case of theclean room.

Accordingly, the clean room and the local facility are particularlysuitable to the production of semiconductors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present, the air filter is manufactured in the samemanner as conventional air filters for use in clean rooms. This is doneby treating glass fibers or organic fibers, such as polytetrafluoroethylene, with a treatment agent containing, for example, a binder madeof an acrylic resin or the like, a non-silicone type water repellent, aplasticizer, and an antioxidant, thereby forming a cloth-like filtermedium, putting the filter medium into a frame of a predetermined sizeand tightly sealing a portion between the frame and the filtrationmedium with a sealing material, in which those not forming gaseousorganic substances during use of the clean room are selected and used asthe treatment agent and the sealing material. Specifically, thetreatment agent is adapted to satisfy the above definitions (a)-(c),while the sealing material is adapted to satisfy the above definitions(e)-(g).

Further, when the fibers for the filter medium are glass fibers, asilicone oil not containing cyclosiloxanes having 10 silicone atoms orless is used, or glass fibers coated with a silicone oil are subjectedto a heat treatment in a clean air stream, to remove cyclosiloxaneshaving 10 silicon atoms or less, so that cyclosiloxanes having 10silicone atoms or less are not contained in the filter medium.

Further, in order that the phosphorus compounds and the boron compoundsare not present in the clean room and the local facility, at least thesurface material for the walls and the floors (only for the walls in thelocal facility not equipped with floors), the filter medium for the airfilter, and the sealing material for tightly sealing a portion betweenthe filter medium and the frame are formed of a material not releasingthe organic phosphorus compounds and the boron compounds in the air.Specifically, as the materials described above, those releasing gaseousorganic phosphorus compounds in an amount of 10 μg or less per 1 g ofthe material by the purge & trap method and leaching the boron compoundsin an amount of 20 μg or less per 1 g of the material after immersing insuper-purified water for 28 days are used.

Details for the mode of practicing the present invention will beexplained below referring to concrete examples.

EXAMPLE 1

In Nos. 1-5 and 7-12, air filters were manufactured by using glassfibers or fluoro-fibers as the filter medium, in which the non-siliconetype water repellent, the plasticizer and the antioxidant contained inthe treatment agent, the main ingredient for the sealing material andthe plasticizer and the antioxidant contained in the sealing materialhad constitutions shown in the following Tables 1 to 3. In No. 6,commercially available ULPA filters were used as they were, and theingredients for each of the constituent materials were analyzed andexamined by the following method.

Abbreviations in each of the tables show the following substances.

K1: Di-2-ethylhexyl sebacate

S1: Stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl) propionate

K2: Dilsodecyl phthalate

S2: 2,2′-methylene-bis (4-ethyl-6-t-butylphenol)

K3: Tris-2-ethylhexyl trimellitate

S3: 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane

K4: 1,3-butylene glycol adipate

S4: 2,6-di-t-butyl-p-cresol

K5: Dioctyl phthalate

S5: 2,6-di-t-butyl-4-ethylphenol

K6: Dibutyl phthalate

K7: Dibutyl adipate

(Fiber for Filter Medium)

In Nos. 1-5, glass fibers for use in commercially available ULPA filters(coated with a silicone oil upon spinning) removed with siloxanes having10 silicon atoms or less by heating in a clean air stream at 120° C. for6 hours were used. When 400 mg of the glass fibers were analyzed by thefollowing P&T (dynamic headspace)-GC/MS method, siloxane having 10silicon atoms or less contained in the glass fibers were less than thedetection limit value by the analyzing method.

In Nos. 6-9, glass fibers for use in commercial ULPA filters (coatedwith a silicone oil upon spinning) were used as they were.

In No. 10, silicone oil KF99, manufactured by Shinetsu Chemical IndustryCo., was charged in a vacuum distillation device and kept at 200° C. ata vacuum degree of 5 mHg to remove low boiling ingredients, by which thesiloxanes having 10 silicon atoms or less contained in the silicone oilwere removed sufficiently to less than the detection limit value by theanalysis using the following P&T-GC/MS method. In the analysis, quartzfibers deposited with several mg of a silicone oil after vacuumdistillation were used as the specimen. Then, glass fibers obtained bycoating the silicone oil not containing siloxanes having 10 siliconatoms or less as the reinforcing material upon spinning were used as thefibers for the filter medium.

In Nos. 11 and 12, fluoro-fibers (polytetrafluoroethylene: PTFE) wereused as the fibers for the filter medium. The fibers are not coated withthe silicone oil.

<P&T (Purge & Trap: Dynamic headspace method)-GC/MS method)>

A predetermined amount of the specimen is filled in a test tube, Whichis heated at 150° C. for 30 min while flowing helium gas to the inside.Volatile ingredients are trapped in a trap tube cooled to −80° C., andthe ingredients in the trap tube are then heated rapidly to 300° C.under a helium gas stream into a gaseous state, and are then introducedinto a GC/MS device.

The GC device is HP-5890A manufactured by Hewlett-Packard Co. and the MSdevice is HP-5970B of the same company. The column for the GC device isHP-ULTRA 2 (OV-5 system) of the same company having 0.2 mm innerdiameter, 25 mm length, and 0.33 μm thickness. The temperature conditionupon measurement by the GC device is as follows.

Initial temperature 40° C.→temperature elevation at a rate of 10°C./min→final temperature 280° C. (kept for 15 min). Further, the carriergas in the GC device is helium, the injection method is a split method,and a split ratio is 1/200. The ionization method for the MS device isan electron impact method and the detection range is 25 to 1000 at m/z.

The quantitative analysis is conducted by preparing a calibration linefor an organic substance identified on every peak for each of theingredients or, if a plurality of peaks appear, all ingredients areindicated using n-decane as a reference substance by the concentrationconverted based on n-decane as a standard according to a calibrationcurve thereof. Thus, the content and the kind of the volatile organicmaterials in the specimen are measured.

(Treating Agent)

In Nos. 1-5 and 7-12, the non-silicone type water repellent, theplasticizer, and the antioxidant shown in each of the tables wereblended at each of the ratios on every sample (values based on 100 partsby weight of the water repellent are indicated as parts by weight in ()in each of the tables), which are dissolved in a 1:1 solvent mixture ofacetone and toluene, and were incorporated with a predetermined amountof an acrylic resin binder. The solution was impregnated into glassfibers spread and overlaid into a sheet-like web of a predeterminedsize, and was dried to prepare a cloth-like filter medium. About 1 g ofthe non-silicone type water repellent was used for the filter medium forone unit of the filter.

(Sealing Material)

Sealing materials were manufactured by blending the main ingredients forthe sealing materials (main agent and curing agent) and plasticizers(plus antioxidant and lubricant in Nos. 1, 2, 6 to 8, 10, 11) shown ineach of the tables at each of the ratios (values based on 100 parts byweight of the main ingredient are indicated as parts by weight in () ineach of the tables) on every sample and the filter medium was placed onand tightly sealed in an aluminum frame (600 mm×600 mm×100 mm, one-halfsize of commercial product) by using the sealing material to prepare airfilters.

In Nos. 1 and 2 using the polyurethane type sealing material, the curingagent and the main ingredient (diisocyanate comprised of methylenediphenyl diisocyanate as the main ingredient) were mixed at a blendingratio that the equivalent amount of active hydrogen in the former wasgreater than the equivalent amount of the isocyanate group in thelatter.

Further, an amine type curing agent was used for No. 4, and a treatmentof removing volatile organic substances (mainly amines remaining aftercuring) was conducted by winding a ribbon heater around the frame aftercuring and heating it at about 130° C. for 4 hours.

For each of the sealing materials, the releasing amount of the organicsubstances was measured by using a portion cutout therefrom three daysafter curing (several ten milligrams) and by analysis using theP&T(Dynamic headspace)-GC/MS method described above. The results arealso shown collectively in each of the tables. For No. 4, themeasurement was conducted for the sealing material after the treatmentof removing the organic substances described above.

(Performance Test for Air Filter: Measurement for Duet RemovingEfficiency)

For the manufactured air filter, particles of dioctyl phthalate (DOP)were blown at a blow rate of 5.3 cm/sec to the entire surface on oneside. The number of DOP particles contained in the air near the filtermedium surface on the blown side (number of particles at the inlet) andthe number of DOP particles contained in the air in the vicinity of thefilter medium surface on the opposite side (number of particles at theexit) were respectively counted by a particle counter. This countingmethod is Judged as satisfactory if the number of particles at the exitis 100 n/ft³ or less and the number of particles at the inlet is 10⁷n/ft³ (that is, if the removing efficiency is 99.999% or higher). Theefficiency for removing dusts for each of the air filters measured bythis method, which is referred to as “COLD DOP Method”, is shown in eachof the tables.

(Gasket)

Each of the obtained air filters was attached to a frame of a blowerfilter unit by way of the gasket shown in each of the tablesrespectively. Further, the releasing amount of the organic substanceswas also measured for the gasket by using a portion cutout therefrom.The results are also shown collectively in each of the tables.

The gasket used is as shown below. G1 was formed by mixing the mainagent and the curing agent of the main ingredient, the plasticizer, theantioxidant, and the lubricant, and then cast molding them. Further,G2-G4 were formed by heat-kneading the rubber material as the mainingredient, the plasticizer, the antioxidant, and the lubricant andextrusion molding them with an extrusion molder. For G5 and G6,commercial products were used.

<G1 (Urethane Rubber Type (1))>

Main ingredient: Two components polyurethane manufactured by NipponPolyurethane Industry Co.

Main agent: PURE MDI (trade name of products).

Curing agent: polyol

Plasticizer: Di-2-ethylhexyl sebacata

Antioxidant: Stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl) propionate

Lubricant: Microcrystalline wax (number of carbon atoms, 30-about 50)

<G2 (Vinyl Chloride Rubber Type)>

Main ingredient: vinyl chloride rubber manufactured by Nippon Zeon Co.

Plasticizer Chlorinated paraffin

Antioxidant: 2,2′-methylene-bis (4-ethyl-6-t-butyl-phenol)

Lubricant: Microcrystalline wax (number of carbon atoms, 34-about 50)<G3 (Butyl Rubber Type)>

Main ingredient: Butyl rubber manufactured by Asahi Sangyo Co.

Plasticizer: 1,3-butylene glycol adipate

Antioxidant: 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane

Lubricant: Microcrystalline wax (number of carbon atoms, 34-about 50)

<G4 (Chloroprene Rubber Type)>

Main ingredient: Neoprene Rubber manufactured by Toso Co.

Plasticizer: 1,3-butylene glycol adipate

Antioxidant: 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane

Lubricant: Microcrystalline wax (number of carbon atoms, 34-about 50)

<G5 (Urethane Rubber Type (2))>

Gasket using liquid MDI, manufactured by Nippon Polyurethane RubberIndustry Co.

<G6 (Urethane Rubber Type (3))>

Gasket using liduld MDI, manufactured by Nippon Polyurethane RubberIndustry Co.

(Clean Room)

Clean rooms were fabricated by using each of the blower filter units,forming wall materials by dry- sealing of partitions finished by bakecoating, and forming floor materials by using stainless steel sheets asthe surface material of a free access floor. The amount of organicsubstances released was 0.1 μg/g or less both for the wall materials andthe floor materials according to the analysis by the P&TDynamicheadsDace) method described above. After 3 days operation of the cleanrooms, silicon wafers of 6 inch diameter were placed and left for 6hours in it, and the amount and the kind of the organic substancesadsorbed on the wafer were analyzed by using the following SWA device.The results are also shown collectively in each of the tables.

<Analysis by SWA Device>

The SWA device is a silicon wafer analyzer (trade name of products)manufactured by G. L. Science Co. having the following trap device, TCT(Thermal Desorption Cold Trap Injector) device, and GC/MS device. Thetrap device is adapted to desorb materials adsorbed on the surface of awafer and collect desorbed ingredients. The TCT device is adapted toheat the ingredients collected by the trap device to 300° C. in a heliumgas stream, then introduce them into a capillary tube cooled to −130° C.by liquid nitrogen and collect them under cooling. The ingredientscollected by the TCT device are rapidly heated to 300° C. in a heliumgas stream and introduced into the GC/MS device.

Referring to the GC/MS device used herein, the GC device is HP-5890A andMS devices is HP-5971A. HP-5 (25 mm length, 0.2 mm inner diameter, 0.33μm film thickness) is used for the column of the GC device andtemperature condition upon measurement by the GC device is as follows.

Initial temperature 80° C. (kept for 10 min)→temperature elevation at arate of 7° C./min→final temperature 300° C. (kept for 10 min).

Other procedures than the above are identical with those in the P&T(Dynamic headspace)-GC/MS method, by which the content and the kind ofthe organic substances adsorbed on the wafer surface are measured.According to this method, analysis is possible to the order of severalng (10⁻⁹ g) per one wafer.

As seen from the results, in Nos. 1-5 and Nos. 10 and 11 correspondingto each of the embodiments of the present invention, gaseous organicsubstances present in the clean room can be reduced and the amount ofthe organic substances adsorbed to the silicon wafer placed in the cleanroom can be reduced to less than {fraction (1/10)} compared with thecase of a conventional ULPA filter (No. 6) or a filter usingplasticizers and antioxidants, etc. of lower molecular weight (Nos. 7-9,12). Also, the dust removing efficiency is higher than 99*999X, whichdoes not deteriorate the performance of the air filter.

EXAMPLE 2

As the floor material, the wall material, the filter medium of the airfilter (prefilter: for external air intake port, main filter for cleanair blown out port), and the sealing material for securing the filtermedium and the frame of the air filter, the following materials wereused in the combination shown in Tables 4 and 5 to fabricate each ofclean rooms. The size (inner size) of each clean room was6,000×7,200×3,700 mm.

(Floor Material)

A vinyl chloride laying sheet (1) (2.0 mm thickness) was prepared byadding an epoxidized soybean oil as a plasticizer,stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate as an antioxidant,aluminum hydroxide as a flame retardant, and stearyl amide ethyleneoxide adduct as an antistatic agent to a polyvinyl chloride resin. Avinyl chloride laying sheet (2) (2.0 mm thickness) is a commerciallyavailable product (antistatic FLOORLIUM, manufactured by Tori Co.).

A floor for a clean room was formed by appending either one of the vinylchloride sheets or a commercially available stainless steel sheet to afree access floor made of aluminum.

(Wall material)

A vinyl chloride cloth (1) (0.28 mm thickness) was prepared by adding1-3-butylene glycol adipate as a plasticizer,2,2-methylene-bis(4-methyl-6-t-butyl phenyl) as an antioxidant, antimonytrioxide as a flame retardant and stearyl amide ethylene oxide adduct asan antistatic agent to a polyvinyl chloride resin. A vinyl chloridecloth(2) (1.0 mm thickness) is a commercially available product (SG 1533manufactured by Sangetsu Co.).

Walls for the clean room were constituted by appending either one of thevinyl chloride clothes to the wall surface, or disposing a partition foruse in a clean room manufactured by COMMANY Co. (partition made of asteel sheet applied with bake coating at the surface).

(Air filter)

As a filter medium for use in prefilters (P.F) and main filters (ULPAfilter: U.F), three kinds of glass fiber filter mediums, (1)-(3), ofdifferent chemical compositions, filter medium made of polyester fibersand filter medium made of fluoro-fibers (PTFE fibers), were provided.

As the sealing material for securing the filter medium to the frame,polyurethane resin type sealing materials (1) and (2) and an epoxy resintype sealing material were provided. The polyurethane type sealingmaterials (1) and (2) were two component sealing materials containingpure MDI 4,4′-Methylene (phenyl isocyanate) diisobyanate at high purity,manufactured by Nippon Polyurethane Industry Co.) as the main agent, andtrioleyl phosphate was blended to the sealing material (1) and tributylphosphate was blended to the sealing material (2) each by 0.3% by weightas the liquefying agent for MDI, other compositions being identical withthose of the sealing materials (1) and (2).

A frame made of aluminum and having an inner size of 600×1200×100 wasused.

The ULPA filter was attached to an opening of a clean room ceiling notusing a gasket after the complete cure of the sealing material, whilethe prefilter was attached to an external air intake port of a ductdirecting to the ceiling after complete cure of the sealing material.

(Method of analyzing each of constituent materials) Each of the surfacematerials of the floor material and the wall material, the filtermedium, and the sealing material for the air filter (three days aftercuring for the sealing material) used was cut out by a predeterminedamount, subjected to qualitative analysis for organic substances andquantitative analysis for organic phosphorous compounds by the P&T-GC/MSmethod shown in Example 1. The boron content was analyzed by thefollowing method. The detection limit value of the quantitative analysisfor the organic phosphorous compound by the method described above is1.0 μg/g.

(Method of Analyzing Boron Content)

A cut out specimen was immersed in a predetermined amount of ultra-purewater (specific resistivity of higher than 18.6 MΩ) for 28 days, theultra-pure water was introduced into an ICP/MS device (model HP-4500 ofHewlett Packard Co.). The inorganic substances which leached out in theultra-pure water were analyzed and the content of boron was determinedquantitatively by using a calibration curve prepared for an aqueousboric acid at a known concentration. The detection limit value for thequantitative analysis by the method was 0.1 μg/g.

(Evaluation of Clean Room)

In each of the clean rooms, external air (fresh air) passing theprefilters and return air from the inside of the clean room were mixedand sent to a chamber at the back of the ceiling, and then passedthrough the ULPA filters at the ceiling and supplied into the cleanroom, where the mixing ratio between the return air and the fresh airwas set to 10:1. Then, each of the clean rooms was operated continuouslyfor two weeks at an air flow rate at the exit from the ULPA filter to0.40 m/s, at a temperature of 23° C., and at a relative humidity of40%., in an unattended state with nothing placed at the inside and,subsequently, air in each of the clean rooms was taken out to analyzeorganic and inorganic substances contained in the air.

For the analysis of the organic substances, 40 liters of air in theclean room were introduced into a TENAX tube (trade name of ChromepackCo.) thereby adsorbing organic ingredients contained in the air. Then,the TENAX tube was installed to a TCT device (refer to Example 1), theorganic ingredients adsorbed to the TENAX tube were taken out by the TCTdevice, were heated, and then were introduced into the GC/MS device. Thedetection limit value for the quantitative analysis by this method were10 ng/m³.

Inorganic substances were analyzed by introducing air in the clean roomat a flow rate of 10 liter per min for 24 hours into an impingercontaining 200 ml of ultra-pure water (specific resistivity of higherthan 18.6 MΩ), leaching the inorganic ingredients contained in the airinto the ultra-pure water, and introducing the ultra-pure water into theICP/MS device (model HP-4500 of Hewlett Packard Co.). The detectionlimit value for the quantitative analysis by this method were 20 ng/m³.

The results for each of the analyses are shown collectively in Tables 4and 5.

As can be seen from the results, in the clean rooms of NOs. 21-24corresponding to the embodiments of the present invention, analysisvalues for the organic phosphorus compounds and the boron compounds inthe clean room air are below the detection limit values. Since theorganic phosphorous compounds and the boron compounds are not present inthe air at the inside of the clean rooms, such clean rooms areparticularly suitable as those used for semiconductor production. On thecontrary, the clean rooms of Nos. 25-28 corresponding to the comparativeexamples of the present invention are not preferred since either theorganic phosphorus compounds or the boron compounds are present in theclean room air, and there is a worry of causing unnecessary doping ofthe clean room for semiconductor production.

In this Example 2, the ULPA filter is attached to the opening of theclean room ceiling without using the gasket. When a urethane rubber typegasket is used, it is desirable to use a phosphoric acid ester having300 or more molecular weight as the liquefying material for diphenylmethane isocyanate, like that in the sealing material for securing thefilter medium to the frame.

EXAMPLE 3

The wall material, the filter medium for the air filter (ULPA filter),and the sealing material for securing the filter medium and the frame ofthe air filter were used in the combination shown in Table 6 tofabricate each of local facilities for use in semiconductor productionapparatus. Each of the constituent materials was analyzed in the samemanner as in Example 2.

Then each of the local facilities was placed in No. 21 clean room inExample 2 and air in the clean room (fresh air and return air mixed andpassed through the ULPA filter in the clean room) was introduced intothe ULPA filter of the local facility for Nos. 31 and 33. Further, forNos. 32 and 34, only the fresh air was introduced into the ULPA filterof the local facility. In this way, after continuous two week operationof each of the local facilities in No. 21 clean room under theconditions described above, air in each of the local facilities wastaken out and the organic substances and inorganic substances containedin the air were analyzed in the same manner as in Example 2.

The results for each analysis were also shown in Table 6.

As seen from the results, in the local facilities of Nos. 31 and 33corresponding to the embodiments of the present invention, analysisvalues for the organic phosphorus compounds and the boron compounds inthe air at the inside of the local facilities are below the detectionlimit values, and since the organic phosphorus compounds and the boroncompounds are not present in the local facilities, such local facilitiesare particularly suitable as the local facility for use in semiconductorproduction. On the contrary, the local facilities of Nos. 32 and 34corresponding to the comparative examples of the present invention arenot desired, since either the organic phosphorus compounds or the boroncompounds are present in the air at the inside of the local facilitiesand there is a worry of causing unnecessary doping for the localfacility used in the semiconductor production.

Also in this Example 3, the ULPA filter is attached to the ceilingopening of the local facility without using gaskets. In a case of usingurethane rubber type gaskets, it is desirable to use a phosphoric acidester having 300 or more weight as the liquefying material for thediphenyl methane isocyanate like that in the sealing material forsecuring the filter medium to the frame.

TABLE 1 No. 1 No. 2 No. 3 No. 4 Fiber Glass fiber for Glass fiber forGlass fiber for Glass fiber for ULPA filter ULPA filter ULPA filter ULPAfilter Silicone oil Si₁₀ or less Si₁₀ or less Si₁₀ or less Si₁₀ or lesssiloxane removed siloxane removed siloxane removed siloxane removedTreating agent Water Synthetic C24 branched Microcrystalline Polyolelfinwax repellent paraffin (C₂₀—C₂₈) higher alcohol wax (C₃₄—C₅₀) (C₂₀—C₂₈)agent [100] Plasticizer Epoxydized K2 (Mw = 447) [5] K3 (Mw = 547) [7]K4 (Mw = 2000-4000) soybean oil [10] (Mw = 1000) [7] Antioxidant S1 (Mw= 520.9) S1 (Mw = 520.9) [2] S2 (Mw = 368.54) [2] S3 (Mw = 544.8) [4]Constitution of sealing material Main ingredient Main 4,4′ Methylene4,4′ Methylene Epoxy resin Epoxy resin agent (phenyl (phenyl (bisphenoltype) (bisphenol type) isocyanate) isocyanate) Curing Polyol type Polyoltype Acid anhydride Amine type (heat agent (methylnadic treated afteracid) curing) Plasticizer K1 (Mw = 427) [5] K1 (Mw = 427) [5] K4 (Mw =2000-4000) Epoxidized [10] soybean oil (Mw = 1000) [10] Antioxidant S2(Mw = 368.54) [3] S2 (Mw = 368.54) [3] Lubricant Synthetic Syntheticparaffin (C₂₀—C₂₈) paraffin (C₂₀—C₂₈) [6] [6] Amount of 4.5 4.5 8.2 7.5organics released from sealing material (μg/g) Kind of gasket G1(urethane Not used G2 (vinyl chloride G3 (butyl rubber rubber type)rubber type type) Amount of not more than 1 5.6 2.7 organics releasedfrom gasket (μg/g) Amount of 28 26 31 20 organics adsorbed on wafer(ng/wafer) Kind of organics Not identifiable Not identifiable Notidentifiable Not identifiable adsorbed on wafer because of each becauseof each because of each because of each small peak small peak small peaksmall peak Particle More than 99.999% More than 99.999% More than99.999% More than 99.999% filtering efficiency

TABLE 2 No. 5 No. 6 No. 7 No. 8 Fiber Glass fiber for Glass fiber forGlass fiber for Glass fiber for ULPA filter ULPA filter ULPA filter ULPAfilter Silicone oil Si₁₀ or less Si₃—Si₁₀ siloxane Si₃—Si₁₀ siloxane Si₃—Si₁₀ siloxane siloxane removed contained contained contained Treatingagent Water repel- Natural paraffin C₉-C₁₆ aliphatic Liquid paraffinLiquid paraffin lent agent (C₂₂—C₃₀) hydrocarbon (C₁₂-C₁₈) (C₁₂-C₁₈)[100] Plasticizer K1 (Mw = 427) [7] K5 (Mw = 391) [7] K5 (Mw = 391) [7]K5 (Mw = 391) [7] Antioxidant S3 (Mw = 544.8) [3] S4 (Mw = 220.4) [3] S4(Mw = 220.4) [2] S5 (Mw = 234) [2] Constitution of sealing material Mainingredient Main Epoxy resin 4,4′ Methylene 4,4′ Methylene 4,4′ Methyleneagent (bisphenol type) (phenyl (phenyl (phenyl isocyanate) isocyanate)isocyanate) Curing Acid anhydride Polyol type Polyol type + Polyoltype + agent phoshate type phosphate type Plasticizer K4 (Mw =2000-4000) K6 (Mw = 278) [7] K5 (Mw = 391) [7] K5 (Mw = 391) [8] [10]Antioxidant Tributylphosphate Tributylphosphate TributylphosphateLubricant C₉—C₁₈ aliphatic Liquid paraffin Liquid paraffin hydrocarbon(C₁₂—C₁₈) [6] (C₁₂-C₁₈) [7] Amount of 8.3 2750 853 792 organics releasedfrom sealing (material (μg/g) Kind of gasket G4 (chloroprene Urethanerubber G5 (urethane Not used rubber type) type rubber type (2)) Amountof 7.3 2630 185 — organics released from gasket (μg/g) Amount of 35 653586 537 organics adsorbed on wafer (ng/wafer) Kind of organics Notidentifiable C₉—C₁₆ aliphatic C₁₂—C₁₈ aliphatic C₁₂—C₁₈ aliphaticadsorbed on wafer because of each hydrocarbon hydrocarbon hydrocarbonsmall peak Si₃—Si₁₀ siloxane Si₃—Si₃₀ siloxane siloxane K5, K6, S4 K5,K6, S4 K5, K6, S4 2-ethylhexanol Tributylphosphate Tributylphosphate2-ethylhexanol 2-ethylhexanol Particle More than 99.999% More than99.999% More than 99.999% More than 99.999% filtering efficiency

TABLE 3 No. 9 No. 10 No. 11 No. 12 Fiber Glass fiber for Glass fiberFluoro fiber Fluoro fiber ULPA filter (PTFE) (PTFE) Silicone oilSi₃—Si₁₀ siloxane Si₁₀ or less Not used Not used contained siloxaneremoved Treating agent Water Liquid paraffin Synthetic Synthetic Liquidparaffin repellent (C₁₂—C₁₈) paraffin (C₂₀—C₂₈) paraffin (C₂₀—C₂₈)(C₁₂—C₁₈ ) agent [100] Plasticizer K7 (Mw = 258) [7] EpoxydizedEpoxydized K5 (Mw = 391) [7] soybean oil [7] soybean oil [7] (Mw = 1000)(Mw = 1000) Antioxidant S4 (Mw = 220.4) [3] S1 (Mw = 520.9) [3] S1 (Mw =520.9) [3] S4 (Mw = 220.4) [2] Constitution of sealing material Mainingredient Main Epoxy resin 4,4′ Methylene 4,4′ Methylene Epoxy resinagent (bisphenol type) (phenyl (phenyl (bisphenol type) isocyanate)isocyanate) Curing Amine type Polyol type Polyol type Amine type agentPlasticizer K6 (Mw = 278) [10] K1 (Mw = 427) [5] K1 (Mw = 427) [5] K6(Mw = 278) [10] Antioxidant S2 (Mw = 368.54) [3] S2 (Mw = 368.54) [3]Lubricant Synthetic para- Synthetic para- ffin (C₂₀—C₂₈) [6] ffin(C₂₀—C₂₈) [6] Amount of 1360 5.3 5.6 584 organics released from sealingmaterial (μg/g) Kind of gasket G6 (urethane G1 (urethane G1 (urethane G6(urethane rubber type (3)) rubber type (1)) rubber type (1)) rubber type(3)) Amount of 168 less than 1 less than 1 168 organics released fromgasket (μg/g) Amount of 820 25 18 483 organics adsorbed on wafer(ng/wafer) Kind of organics C₁₂—C₁₈ aliphatic Not identifiable Notidentifiable C₉—C₁₈ aliphatic adsorbed on wafer hydrocarbon, because ofeach because of each hydrocarbon, Si₃—So₁₀ siloxane, small peak smallpeak K6, S4, K7, K6, S4 Tributylphosphate Triethylene tetramineTributylphosphate Particle More than 99.999% More than 99.999% More than99.999% More than 99.999% filtering efficiency

TABLE 4 No. 21 No. 22 No. 23 No. 24 Clean Room constituent member Floorsurface material Material Stainless steel Stainless steel Vinyl chlorideVinyl chloride sheet sheet sheet (1) sheet (1) Boron content belowdetection below detection below detection below detection (μg/g) limitvalue limit value limit value limit value Organic below detection belowdetection below detection below detection phosphorus limit value limitvalue limit value limit value content (μg/g) Wall surface materialMaterial Coated steel Coated steel Vinyl chloride Vinyl chloride plateplate cloth (1) cloth (1) Boron content below detection below detectionbelow detection below detection (μg/g) limit value limit value limitvalue limit value Organic below detection below detection belowdetection below detection phosphorus limit value limit value limit valuelimit value content (μg/g) P.F filter medium Material Glass fiber (1)Polyester fiber Glass fiber (1) Polyester fiber Boron content 15 belowdetection 15 below detection (μg/g) limit value limit value Organicbelow detection below detection below detection below detectionphosphorus limit value limit value limit value limit value content(μg/g) U.F filter medium Material Glass fiber (1) Glass fiber (1) Glassfiber (1) PTFE fiber Boron content 15 15 15 below detection (μg/g) limitvalue Organic below detection below detection below detection belowdetection phosphorus limit value limit value limit value limit valuecontent (μg/g) sealing agent Material Polyurethane Polyurethane Epoxyresin Expoxy resin resin type (1) resin type (1) type type Boron contentbelow detection below detection below detection below detection (μg/g)limit value limit value limit value limit value Organic TrioleylTrioleyl below detection below detection phosphorus phosphate phosphatelimit value limit value content (μg/g) 15 15 Boron content in cleanbelow detection below detection below detection below detection room air(ng/m³) limit value limit value limit value limit value Organicphosphorus below detection below detection below detection belowdetection compound content in limit value limit value limit value limitvalue clean room air (ng/m³)

TABLE 5 No. 25 No. 26 No. 27 No. 26 Clean Room constituent member Floorsurface material Material Stainless steel Stainless steel Stainlesssteel Vinyl chloride sheet sheet sheet sheet (1) Boron content belowdetection below detection below detection below detection (μg/g) limitvalue limit value limit value limit value Organic below detection belowdetection below detection Tris- phosphorus limit value limit value limitvalue (β-chloroethyl) content (μg/g) phosphate 14 Wall surface materialMaterial Coated steel Coated steel Coated steel Vinyl chloride plateplate plate cloth (2) Boron content below detection below detectionbelow detection below detection (μg/g) limit value limit value limitvalue limit value Organic below detection below detection belowdetection Tris- Phosphorus limit value limit value limit value(β-chloroethyl) content (μg/g) phosphate 20 P.F filter medium MaterialGlass fiber (3) Glass fiber (2) Polyester fiber Polyester fiber Boroncontent 52 24 below detection below detection (μg/g) limit value limitvalue Organic below detection below detection below detection belowdetection phosphorus limit value limit value limit value limit valuecontent (μg/g) U.F filter medium Material Glass fiber (3) Glass fiber(2) Glass fiber (2) PTFE fiber Boron content 52 24 24 below detection(μg/g) limit value Organic below detection below detection belowdetection below detection phosphorus limit value limit value limit valuelimit value content (μg/g) sealing material Material PolyurethanePolyurethane Epoxy resin Epoxy resin resin type (2) resin type (2) typetype Boron content below detection below detection below detection belowdetection (μg/g) limit value limit value limit value limit value OrganicTributyl Tributyl below detection below detection phosphorus phosphatephosphate limit value limit value content (μg/g) 100 100 Boron contentin clean 120 70 32 below detection room air limit value Organicphosphorus Tributyl Tributyl below detection Tris- compound content inphosphate phosphate limit value (β-chloroethyl) clean room air 150 140phosphate 250

TABLE 6 No. 31 No. 32 No. 33 No. 34 Local facility constituent materialWall material Material Coated steel Stainless steel Coated steelStainless steel plate sheet plate sheet Boron content below detectionbelow detection below detection below detection (μg/g) limit value limitvalue limit value limit value Organic below detection below detectionbelow detection below detection phosphorus limit value limit value limitvalue limit value content (μg/g) U.F filter medium Material Glass fiber(1) Glass fiber (1) Glass fiber (3) Glass fiber (3) Boron content 15 1552 52 (μg/g) Organic below detection below detection below detectionbelow detection phosphorus limit value limit value limit value limitvalue content (μg/g) sealing material Material Polyurethane PolyurethanePolyurethane Polyurethane resin type resin type resin type resin typeBoron content below detection below detection below detection belowdetection (μg/g) limit value limit value limit value limit value OrganicNot contained Not contained Tributyl Tributyl phosphorus phosphatephosphate content (μg/g) 430 430 Boron content in air below detectionbelow detection 105 80 in local facility limit value limit value (ng/m³)Organic phosphorus below detection below detection Tributyl Tributylcompound content in limit value limit value phosphate phosphate air inlocal facility 250 250 (ng/m³)

INDUSTRIAL APPLICABILITY

As described above according to the air filter of the present invention,since the releasing amount of gaseous organic substances can bedecreased in the clean room or the local facility having the filterdisposed to an air introduction path, the air filter according to thepresent invention is suitable to a clean room or a local facility, forexample, of semiconductor production factories.

Since the releasing amount of the gaseous organic substances is reducedin the clean room and the local facility according to the presentinvention having the air filter described above, if the clean room orthe local facility (semiconductor production apparatus) is used, forexample, in the industry of semiconductor production, the adsorptionamount of the organic substances to silicon wafers is decreased toimprove the yield.

Further, since unnecessary doping to silicon wafers may not be caused inthe clean room and the local facility of the present invention in whichthe organic phosphorus compounds and boron compounds are not present,they are particularly suitable to the clean room and the local facilityfor use in semiconductor production.

What is claimed is:
 1. A clean room for manufacturing semiconductors,the clean room having an air filter, the air filter comprising: a filtermedium; and a sealing material; wherein the filter medium does notrelease gaseous organic substances more than about 10 μg/g-samplemeasured by dynamic headspace-gas chromatography/mass spectroscopy at150° C. for 30 minutes; and wherein the sealing material does notrelease gaseous organic substances more than about 50 μg/g-samplemeasured by dynamic headspace-gas chromatography/mass spectroscopy at150° C. for 30 minutes; wherein the gaseous organic substances aredibutyl phthalate, dioctyl phthalate, 2-ethylhexyl adipate,2,6-di-t-butyl-p-cresol, hydrocarbons having fewer than 18 carbon atoms,cyclosiloxanes having fewer than 9 silicon atoms, and tributylphosphate.
 2. A local facility for manufacturing semiconductors, thelocal facility having an air filter, the air filter comprising: a filtermedium; and a sealing material; wherein the filter medium does notrelease gaseous organic substances more than about 10 μg/g-samplemeasured by dynamic headspace as chromatography/mass spectroscopy at150° C. for 30 minutes; and wherein the sealing material does notrelease gaseous organic substances more than about 50 μg/g-samplemeasured by dynamic headspace-gas chromatography/mass spectroscopy at150° C. for 30 minutes; wherein the gaseous organic substances aredibutyl phthalate, dioctyl phthalate, 2-ethylhexyl adipate,2,6-di-t-butyl-p-cresol, hydrocarbons having fewer than 18 carbon atoms,cyclosiloxanes having fewer than 9 silicon atoms, and tributylphosphate.
 3. The clean room as defined in claim 1, wherein the cleanroom has walls and floors fabricated with building materials releasinggaseous organic substances in an amount of 50 μg or less per 1 gmeasured by dynamic headspace-gas chromatography/mass spectroscopy at150° C. for 30 minutes, and wherein the air filter is attached byinterposing an organically based gasket between the air filter and anopening for attachment, wherein the gasket releases gaseous organicsubstances in an amount of 50 μg or less per 1 g measured by dynamicheadspace-gas chromatography/mass spectroscopy at 150° C. for 30minutes; wherein the gaseous organic substances are dibutyl phthalate,dioctyl phthalate, 2-ethylhexyl adipate, 2,6-di-t-butyl-p-cresol,hydrocarbons having fewer than 18 carbon atoms, cyclosiloxanes havingfewer than 9 silicon atoms, and tributyl phosphate.
 4. A clean room formanufacturing semiconductors, the clean room having an air filter, theair filter comprising: a filter medium formed into a fiber layer bytreating fibers with a treatment agent wherein the treatment agentcomprises a non-silicone water repellent agent having a main componentselected from the group consisting of aliphatic hydrocarbons having 20carbon atoms or more, and higher alcohols having 18 carbon atoms ormore; a frame containing the filter medium; and a sealing materialfirmly sealing the frame and the filter medium; wherein the filtermedium and the sealing material substantially do not release gaseousorganic substances.
 5. A clean room for manufacturing semiconductors,the clean room having an air filter, the air filter comprising: a filtermedium being formed into a fiber layer by treating fibers with atreatment agent, wherein the treatment agent comprises a plasticizerhaving a main component selected from the group consisting of carboxylicacid esters, polyesters, and epoxy fatty acid esters having a molecularweight of 400 or more; a frame containing the filter medium; and asealing material which firmly seals the frame and the filter medium;wherein the filter medium does not release gaseous organic substancesmore than about 10 μg/g-sample measured by dynamic headspace-gaschromatography/mass spectroscopy at 150° C. for 30 minutes; and whereinthe sealing material does not release gaseous organic substances morethan about 50 μg/g-sample measured by dynamic headspace-gaschromatography/mass spectroscopy at 150° C. for 30 minutes.
 6. A cleanroom for manufacturing semiconductors, the clean room having an airfilter, the air filter comprising: a filter medium being formed into afiber layer by treating fibers with a treatment agent, wherein thetreatment agent comprises an antioxidant having a main componentselected from the group consisting of phenolic compounds havingmolecular weights of 300 or more; a frame containing the filter medium;and a sealing material which firmly seals the frame and the filtermedium; wherein the filter medium does not release gaseous organicsubstances more than about 10 μg/g-sample measured by dynamicheadspace-gas chromatography/mass spectroscopy at 150° C. for 30minutes; and wherein the sealing material does not release gaseousorganic substances more than about 50 μg/g-sample measured by dynamicheadspace-gas chromatography/mass spectroscopy at 150° C. for 30minutes.
 7. A clean room for manufacturing semiconductors, wherein theclean room has walls and floors fabricated with building materials, andwherein the clean room has an air filter, the air filter comprising afilter medium, a frame, and a sealing material tightly sealing the frameand the filter medium, and wherein the filter medium is formed from amaterial selected from the group consisting of glass fibers, fluorofibers, and polyester fibers, the sealing material is formed from amaterial selected from the group consisting of epoxy resins andpolyurethane resins, and further wherein the building materials, thefilter medium and the sealing material release gaseous organicphosphorus compounds in an amount of 10 μg or less per 1 g of thematerial measured by dynamic headspace-gas chromatography/massspectroscopy at 150° C. for 30 minutes, and leaches boron compounds inan amount 20 μg or less per 1 g of the material after immersing inultra-pure water for 28 days.
 8. A clean room for manufacturingsemiconductors, wherein the clean room has walls and floors fabricatedwith building materials, and wherein the clean room has an air filter,the air filter comprising a filter medium, a frame, and a sealingmaterial tightly sealing the frame and the filter medium, And furtherwherein the building materials, the filter medium and the sealingmaterial release gaseous organic phosphorus compounds in an amount of 10μg or less per 1 g of the material measured by dynamic headspace-gaschromatography/mass spectroscopy at 150° C. for 30 minutes, and leachesboron compounds in an amount 20 μg or less per 1 g of the material afterimmersing in ultra-pure water for 28 days; wherein the sealing materialis a polyurethane resin sealing material and contains diphenyl methanediisocyanate as a diisocyanate constituting the main ingredient thereofand, when a phosphoric acid ester is contained as a liquefying agenttherefor, the phosphoric acid ester has a molecular weight of 300 ormore.
 9. A clean room for manufacturing semiconductors, wherein theclean room has walls and floors fabricated with building materials, andwherein the clean room has an air filter, the air filter comprising afilter medium, a frame, and a sealing material tightly sealing the frameand the filter medium, and further wherein the building materials, thefilter medium and the sealing material release gaseous organicphosphorus compounds in an amount of 10 μg or less per 1 g of thematerial measured by dynamic headspace-gas chromatography/massspectroscopy at 150° C. for 30 minutes, and leaches boron compounds inan amount 20 μg or less per 1 g of the material after immersing inultra-pure water for 28 days; wherein a phosphoric acid ester used as aliquefying agent for the sealing material is selected from the groupconsisting of tri-2-ethylhexyl phosphate, tributoxyethyl phosphate,trioleyl phosphate, triphenyl phosphate, tricresol phosphate, trixylenylphosphate, cresyl phenyl phosphate, xylenyl diphenyl phosphate,2-ethylhexyldiphenyl phosphate, aromatic condensed phosphoric acidester, tris-tridecyl phosphite, and triphenyl phosphite.
 10. A localfacility for manufacturing semiconductors, wherein the local facilityhas walls, floors, a filter medium for an air filter, and a sealingmaterial for tightly sealing the filter medium and a frame, and furtherwherein the filter medium and the sealing material release gaseousorganic phosphorus compounds in an amount 10 μg or less per 1 g of thematerial measured by dynamic headspace-gas chromatography/massspectroscopy at 150° C. for 30 minutes, and leaches boron compounds inan amount 20 μg or less per 1 g of the material after immersing inultra-pure water for 28 days; wherein a phosphoric acid ester used as aliquefying agent for the sealing material is selected from the groupconsisting of tri-2-ethylhexyl phosphate, tributoxyethyl phosphate,trioleyl phosphate, triphenyl phosphate, tricresol phosphate, trixylenylphosphate, cresyl phenyl phosphate, xylenyl diphenyl phosphate,2-ethyihexyldiphenyl phosphate, aromatic condensed phosphoric acidester, tris-tridecyl phosphite, and triphenyl phosphite.
 11. A cleanroom and a local facility for manufacturing semiconductors, wherein atleast one of a surface material for walls and floors, a filter mediumfor an air filter, and a sealing material for tightly sealing the filtermedium and a frame are formed of a material substantially not releasingorganic phosphorus compounds and boron compounds in the air; wherein thesealing material is a polyurethane resin sealing material and containsdiphenyl methane diisocyanate as a diisocyanate constituting the mainingredient thereof and, when a phosphoric acid ester is contained as aliquefying agent therefor, the phosphoric acid ester has a molecularweight of 300 or more.
 12. The clean room and the local facility asdefined in claim 11, wherein the phosphoric acid ester used as theliquefying agent is selected from the group consisting oftri-2-ethylhexyl phosphate, tributoxyethyl phosphate, trioleylphosphate, triphenyl phosphate, tricresol phosphate, trixylenylphosphate, cresyl phenyl phosphate, xylenyl diphenyl phosphate,2-ethylhexyldiphenyl phosphate, aromatic condensed phosphoric acidester, tris-tridecyl phosphite, and triphenyl phosphite.
 13. The cleanroom as defined in claim 4 wherein the filter medium and the sealingmaterial do not release gaseous organic substances more than about 50μg/g-sample measured by dynamic headspace-gas chromatography/massspectroscopy at 150° C. for 30 minutes.